Photoelectrical response of hybrid graphene-PbS quantum dot devices

Hybrid graphene-PbS quantum dot devices are fabricated on an n-type silicon substrate capped with a thin SiO2 layer and are characterized by photoelectrical measurements. It is shown that the resistance of the graphene channel in the devices exhibits detectable changes when a laser beam is switched on and off on the quantum dots. The model that explains the observed photoresponse phenomenon is illustrated. We also show that the photoresponse signal, i.e., the photoinduced change in the resistance of the graphene channel can be tuned in both magnitude and sign with a voltage applied to the back gate of the devices and is related to the derivative of the transfer characteristics of the graphene channel. Our work shows that the simple hybrid graphene-PbS quantum dot devices can be employed for photodetection applications. (C) 2013 AIP Publishing LLC.